Published Date: 1999-03-29 23:50:00
Subject: PRO/AH/EDR> Influenza H5N1, avian - China (Hong Kong)
Archive Number: 19990329.0490

INFLUENZA H5N1, AVIAN - CHINA (HONG KONG)
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See Also

Influenza A/H5N1, clinical findings
980213223608
Influenza H5N1, avian - China (04)
980119231358
Influenza H5N1, human - China (Hong Kong) (04) 980116000038
Influenza H5N1, human - China (Hong Kong): report 980307234341
Influenza H5N1, human - China(Hong Kong):serosurvey (02) 980224205434
Influenza H5N1, new vaccine development - USA 980205230946
Date: Sat, 27 Mar 1999 08:59:00 -0600
From: Clyde Markon <docmarkon@worldnet.att.net>
Source: South China Morning Post, Fri 26 Mar 1999

Bird flu strain found in Western market
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The government has confirmed finding a strain
of the H5N1 bird flu virus in water fowl at a local wholesale market -- the
first discovery since its ''distant relative'' killed six people in the
territory. However, health authorities say the isolated incident did not
herald the virus's return. The Agriculture and Fisheries Department (AFD)
said on Friday the SAR would stop importing poultry from contaminated farms
on the mainland, if any were spotted.
World-renowned virologist Professor Robert Webster, now visiting Hong Kong,
said there was no cause for alarm as the recent discovery -- found in either
geese or duck droppings -- was the ''great-grandparent'' of the H5N1 virus
spread among local chickens and humans in 1997. He said it was still
doubtful the virus could infect humans -- the chances would be ''close to
nothing''. The Department of Health interviewed ten poultry workers at
Western Wholesale Poultry Market, where the virus was found. None of them
showed any symptoms of infection.
Dr Mak Kwok-hang, the Department of Health's consultant in community
medicine, said ducks and geese were still safe to eat as long as they were
well-cooked. ''There is no evidence to show the virus can infect humans,
but as it is again H5 virus, we have to be on high alert. We must not
overlook its importance.''
Animal Quarantine authorities in Shenzhen plan to step up surveillance of
bird flu virus in poultry. And AFG said the find clearly demonstrated the
worth of the surveillance systems used by the Agriculture and Fisheries
Department. An AFG spokesman said: "The successful isolation demonstrates
that AFD's stringent import control and monitoring systems are working well.
''Testing and regular monitoring of birds at all levels of production --
local farms, imported birds and wholesale and retail markets will continue
as a regular measure.''
[By Ella Lee
--
ProMED-mail
<promed@usa.healthnet.org>
***
Comment by:
David M. Morens, M.D. <promed@usa.healthnet.org>

This report from Hong Kong emphasizes our growing understanding of
influenza A viruses as essentially en- and epizootic infections with highly
complex cycles and occasional species-switches into humans. The temporal
association between epizootic influenza (classically in pigs or horses) and
human epidemics has been known and extensively documented for centuries.
Apparently, epizootic cycles serve as factories for engineering new viruses,
some of which, through various and imperfectly understood mechanisms, may
wind up infectious for humans and capable of causing epidemics or pandemics.
The principal enzootic hosts are aquatic waterfowl, e.g., ducks. These
birds do not have apparent illness but experience infection of columnar
epithelial cells of the gastrointestinal tract and transmit virus via the
"fecal-oral" route (like polioviruses in humans), not via respiratory
spread. The different waterfowl H (hemagglutinin) types exhibit different
tropisms for cells of different host species. For example, there has been
an observed tendency for H1 types to infect pigs, and for H3 types to infect
horses. H5 and H7 types seem especially liable to spread into domestic
poultry (e.g., chickens), as was the case with the H5N1 epizootic/epidemic
in Hong Kong in 1997. This was referred to in the lay press as "bird flu"
or "avian flu". Similarities between viruses found in domestic fowls and
humans suggest that fowl-to-human transmission may be an important pathway
by which influenza viruses escape from their enzootic cycles to become human
pathogens. What we seem to have been seeing in Hong Kong in the past two
years is the tip of a very big epizootiologic iceberg.
In view of the minimal information made public so far about the H5N1
identification in Hong Kong, it is reassuring that Dr. Robert Webster, a
recognized authority, finds "no cause for alarm". Presumably the isolation
(or identification) merely reflects active epizootiologic surveillance.
Possibly the newly identified H5N1 contains only avian influenza genes, and
thus might be less likely to cause a pandemic. We need to know more,
however, about where human viruses come from, and about the inter-species
evolution and "natural history" of influenza viruses as they climb pathways
from enzootic viruses of waterfowl to virulent epidemic strains. The sudden
emergence of the 1918 H1N1-like virus (which killed 25 million people within
a year), and of the H1N1-like "swine influenza" virus of 23 years ago (which
failed to spread globally but created a public health fiasco in the United
States) are important cautionary tales that are still misunderstood, in
part, because of incomplete knowledge of influenza epizootiology.
It should be pointed out that the deadly 1968 "Hong Kong flu"
which supposedly killed 46 500 persons (almost certainly
an underestimate), is not closely related genetically or epidemiologically
to the H5N1 viruses found in Hong Kong in the past two years. The 1968
virus was a human H3N2 strain. Its descendants have circulated continually
for over 30 years, and are still associated with influenza outbreaks and
fatalities worldwide.
The recent H5N1 identification should remind us about the woeful lack of
international preparedness to respond effectively to the continual threat of
emergent influenza and of pandemic spread. This is an unfortunate irony,
given that influenza is near or at the top of almost every expert's
"doomsday list" of emerging infectious diseases. Yet international research
monies are so minuscule that they are often dwarfed by monies for rare
diseases without serious fatal pandemic potential. Public health dogma and
surveillance mechanisms are anachronisms from an earlier era. Poorly
efficacious vaccines, unproven in their capacity to control fatal pandemics,
are endorsed to the exclusion of better vaccines and other prevention
options.
Furthermore, the epizootiology of the influenza viruses has been
too little studied, determinants of species switches into humans not fully
characterized, and epizootiologic surveillance much too limited. (But maybe
Hong Kong is doing a better job in this area than most of the rest of the
world).
...........................jw

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